1. Field of the Invention
This invention relates to methods and apparatus for use in protecting electric power transmission systems against faults.
2. Description Of the Prior Art
It has previously been proposed to detect the occurrence of a fault in a power transmission system and identify the type of fault which has occurred (i.e. phase-to-ground or phase-to-phase etc.) using fault signals. By a fault signal is meant a signal which arises as a consequence of a fault, that is, a signal representing the difference between post-fault and pre-fault values of any particular quantity.